How to add ambient light when using cycles render?
In a typical photographic situation, you would add fill light from a soft / broad source. This could be above your object in question, or a fill light lower down and in front. Using an area light allows you to get the softer breadth required to avoid hard shadows.

Light ratios also tend to be completely whacked unless you are using a viewing transform that emulates a more photographic range of light as well, typically over-crunching the shadow data, and horrifically crimping the highlight data that is in an image. If you are interested, have a look at this question.